The present invention is related to a method for monitoring layer uniformity of sputter coating, and in particular to an in-situ method for monitoring layer uniformity of sputter coating based on intensity distribution of plasma spectrum.
Uniformity is a very important requirement in the fabrication of products when thin-film deposition is needed. In almost all practices, film uniformity can only be characterized after an enormous amount of tests and measurement were conducted. Some works on in-situ measurement of film thickness have been reported, but none could resolve thickness distribution.
U.S. Pat. No. 4,859,277 discloses a method for measuring the concentration profile of an active species across the surface of a semiconductor slice in a plasma reactor, so that uniformity of etch and deposition across the surface of the semiconductor slice can be assured. However, the semiconductor slice very often is kept moving in a processing chamber during etching or depositing, and thus measuring the concentration profile of the active species across the surface of the semiconductor slice as taught in the method of U.S. Pat. No. 4,859,277 is difficult to be carried out.
A primary objective of the present invention is to provide a real-time film uniformity monitoring method for thin-film deposited by sputtering or evaporation.
Another objective of the present invention is to provide a method for adjusting deposition conditions of a thin film deposited by sputtering or evaporation based on a real-time film uniformity monitoring method.
In order to accomplish the objectives of the present invention a first method for in-situ monitoring layer uniformity of sputter coating provided by the present invention comprises the following steps, wherein the sputter coating is deposited on a surface of a substrate inside a reaction chamber having a target opposite to said substrate and a low pressure working gas therein:
a) measuring intensity of plasma emission light along an axis on a surface parallel to said target, wherein said plasma emission light is generated by sputtering said target;
b) splitting said intensity of plasma emission light to obtain an intensity distribution of a predetermined wavelength of an element constituting said target along said axis and an intensity distribution of a wavelength of said working gas adjacent to said predetermined wavelength along said axis;
c) normalizing said intensity distribution of said predetermined wavelength of said element with said intensity distribution of said adjacent wavelength of said working gas to obtain a normalized intensity distribution; and
d) comparing said normalized distribution with a standard normalized distribution of an uniform sputter coating obtained according to steps a), b) and c) in advance, so that the layer uniformity of said sputter coating deposited on said surface of said substrate is in-situ monitored, wherein said uniform sputter coating has a desired layer uniformity directly measured by an instrument, and is deposited under sputtering conditions same as those of said sputter coating under in-situ monitoring.
In step c) of the first method of the present invention, said normalizing comprises dividing an intensity of said predetermined wavelength of said element at a position of said axis by an intensity of said adjacent wavelength of said working gas at the same position of said axis.
In the first method of the present invention, said plasma emission light generated by sputtering said target in step a) is cylindrically symmetric on said surface parallel to said target.
A second method for in-situ monitoring layer uniformity of sputter coating based on intensity distribution of plasma spectrum according to the present invention comprises the following steps:
a) measuring intensity of plasma emission light along an axis on a surface parallel to said target, wherein said plasma emission light is generated by sputtering said target;
b) splitting said intensity of plasma emission light to obtain an intensity distribution of a predetermined wavelength of an element constituting said target along said axis and an intensity distribution of a wavelength of said working gas adjacent to said predetermined wavelength along said axis;
c) deconvoluting the two resulting intensity distributions from step b) to obtain an intensity distribution of said predetermined wavelength of said element along a radius of said surface parallel to said target and an intensity distribution of said wavelength of said working gas adjacent to said predetermined wavelength along said radius of said surface parallel to said target, respectively;
d) normalizing said intensity distribution of said predetermined wavelength of said element along said radius with said intensity distribution of said adjacent wavelength of said working gas along said radius to obtain a normalized intensity distribution; and
e) comparing said normalized distribution with a standard normalized distribution of an uniform sputter coating obtained according to steps a), b), c) and d) in advance, so that the layer uniformity of said sputter coating deposited on said surface of said substrate is in-situ monitored, wherein said uniform sputter coating has a desired layer uniformity directly measured by an instrument, and is deposited under sputtering conditions same as those of said sputter coating under in-situ monitoring.
A third method for in-situ monitoring layer uniformity of sputter coating based on intensity distribution of plasma spectrum according to the present invention is similar to the second method except step e) is replaced by the following:
exe2x80x2) calculating the layer uniformity of said sputter coating deposited on said surface of said substrate by using the resulting normalized distribution from step
d). Preferably, said calculating in step exe2x80x2) is carried out by using the n-th power of cosine law model and the geometric relationship between a substrate and a target.
Said measuring in step a) of the methods of the present invention preferably is carried out by scanning said plasma emission light along said axis on said surface parallel to said target with an optical fiber outside said reaction chamber.
In step d) of the second and third methods of the present invention, said normalizing comprises dividing an intensity of said predetermined wavelength of said element at a value of said radius by an intensity of said adjacent wavelength of said working gas at the same value of said radius.
In step c) of the second and third methods of the present invention, said deconvoluting preferably is carried out by using Abel Inversion, wherein an intensity distribution of a wavelength of a plasma emission light at a radius r on a surface, inten (r), is obtained by the following formula:       inten    ⁢          xe2x80x83        ⁢          (      r      )        =            1      π        ⁢                  ∫        r        R            ⁢                                                                  ⅆ                Inten                            ⁢                              xe2x80x83                            ⁢                              (                x                )                                                    ⅆ              x                                                                          x                2                            -                              r                2                                                    ⁢                  xe2x80x83                ⁢                  ⅆ          x                    
wherein r is a variable representing a value of a radius of the plasma emission light on said surface, R is an assumed radius of the plasma emission light on said surface, x is a variable representing a position of x-axis, and Inten (x) is an intensity of said wavelength of said plasma emission light on said surface, wherein said plasma emission light is cylindrically symmetric on said surface.
In the method of the present invention the intensity distribution of plasma spectrum is measured across a surface above the target, so that the method of the present invention is applicable to deposition methods wherein the substrate to be deposited is kept moving in the processing chamber, and particularly the method of the present invention is applicable to deposition methods wherein more than one substrates are to be deposited in the processing chamber.